1. Field of the Invention
The present invention relates to an ATM switch, and more particularly, to ATM switching apparatus and method in which a multicast is implemented by masking at least one or more destination nodes with fixed bit.
2. Background of the Related Art
Generally, asynchronous transfer mode (ATM) technology processes data communication using a switching technique which is employed in voice communication.
The ATM uses a virtual channel circuit switching and transfers data on cells having fixed-length 53-byte unit. In other words, the ATM is a switch for transferring cells to destination addresses via proper output ports with reference to a predetermined transmission table based on virtual path identifier/virtual channel identifier (VPI/VCI) values existing in a header of the cell inputted through an input port.
FIG. 1 is a view showing a standard construction format of a related art ATM cell. The ATM cell is generally divided into a 48-byte payload on which data is loaded and a 5-byte header on which control information is loaded. The header includes a generic flow control (GFC) indicating traffic adjusting information, a VPI/VCI for setting virtual path/virtual channel, a payload type (PI) used to indicate the presence of user information, a cell loss priority (CLP) indicating a discard priority of cells, and a header error check (HEC) used to detect a head error.
In order to implement multicasting communications in broadband integrated services digital network (BISDN) which uses standard ATM cells having the header constructed as above, one input source should be duplicated as many times as the number of output points and then routed to designated output points. Among methods proposed to implement these functions, typical is a duplication network in which outputted cells are fed back and again buffered by an input buffer. At this time, a cell delay occurs which degrades a performance of ATM switch.